A novel wavelength-division multiplexer using grating-assisted two-mode interference

A novel design of wavelength-division multiplexer based on two-mode interference assisted by a highly dispersive grating structure is two-dimensionally simulated and analyzed using finite-difference time-domain method. We show that the designed grating waveguide provides a mode-dependent reflection spectrum which can be used to modify the beat lengths of the two selected wavelengths 1342 and 1560 nm, so that they can be divided in a very short distance about 48 /spl mu/m. Simulation results show that contrasts /spl sim/12 dB and insertion losses about 2 dB could be achieved.     

基于格图像的康托集分维与泛逻辑运算

对康托集的研究一直是分形领域的经典而又热点的课题。本文尝试用一种新的模式——“格图像”来研究康托集的分形特性,给出了康托集的格图像构造与分形维数计算方法,计算表明：康托集的自相似分维是格图像分维的特例,格图像分维是自相似分维的扩展。文章首次在分形领域引入泛逻辑的概念,给出了基于格图像的康托集的泛逻辑“与,或,非”运算模型,它不仅考虑了集合的代数列度大小。而且考虑了在参考格中的几何位置关系,这给分形图像的研究提供了一种新的思路,同时也拓展了泛逻辑学的应用领域。     

蕈露的毒性研究

蕈露作为一种高级营养饮料,由北京市食品研究所研制成功。我们对其进行了急性毒性、蓄积毒性及诱变性的研究。结果小鼠的最大耐受量为275ml/kg,大鼠LD50大于230ml/kg。蓄积毒性很低,小鼠骨髓微核试验,Ames试验及精子畸变分析均为阴性,未发现有诱变性。因此,我们认为蕈露对人体健康无任何明显有害作用,是安全可靠的,可以做为饮料饮用。     

Low-Temperature Heat Capacities and Standard Molar Enthalpy of Formation of Potassium Benzoate C<Subscript>7</Subscript>H<Subscript>5</Subscript>O<Subscript>2</Subscript>K(s)

Potassium benzoate C₇H₅O₂K (CAS Registry No. 582-25-2) was synthesized by the method of liquid phase reaction. Chemical and elemental analyses, FTIR, and X-ray powder diffraction (XRD) techniques were applied to characterize the composition and structure of the compound. Low-temperature heat capacities of the compound were measured by a precision automated adiabatic calorimeter over the temperature range from 78 K to 398 K. A polynomial equation of the heat capacities as a function of temperature was fitted by the least-squares method. Smoothed heat capacities and thermodynamic functions of the compound were calculated based on the fitted polynomial. In accordance with Hess’s law, a reasonable thermochemical cycle was designed, and 100 mL of 1 mol · dm⁻³ NaOH solution was chosen as the calorimetric solvent. The standard molar enthalpies of dissolution for the reactants and products of the supposed reaction in the selected solvent were measured by an isoperibol solution-reaction calorimeter. Finally, the standard molar enthalpy of formation of the title compound C₇H₅O₂K (s) was derived to be -(610.94 ± 0.77) kJ · mol⁻¹.     

晶格失配对GaAsSb/InP异质结中合金拉曼散射的温度依赖特性的影响

通过在3～300 K的低温变温拉曼光谱的测量,对不同Sb组分的GaAsSb/InP异质结中的由Sb组分引起的声子非谐效应进行了拉曼散射的研究。实验发现,随着温度的降低,长光学声子峰位向高波数移动,当温度低于100 K时,变化趋于平缓。分别利用三声子模型和四声子模型计算模拟了光学声子和温度的依赖关系,并和实验结果对比发现,与三声子模型相比,四声子模型与实验数据符合更好,表明温度依赖的拉曼散射峰位的变化必须考虑四次声子非谐振动。相对于晶格失配的样品S1（Sb=37.9%）和S3（Sb=56.2%）,获得的声子非谐度在晶格匹配的样品S2（Sb=47.7%）中是最小的,同时通过对声子线宽的研究表明S2中声子寿命是最长的。结合低温光致发光的实验结果,证实了GaAsSb合金晶格振动的声子非谐效应和声子寿命不仅受合金无序散射的影响,同时受到和衬底晶格失配引入的线缺陷和缺陷的声子散射影响。     

永磁同步电机高精度转速控制方法综述

电机转速精度是伺服系统的重要性能指标,传统PI控制已不能满足伺服系统的高精度要求. 将先进控制策略应用于永磁同步电机是伺服系统发展的趋势. 本文介绍了永磁同步电机的精确测速方法和先进控制策略在电机转速系统中的应用,分析了各种方法的优缺点和适用范围,综述了最新的研究成果和有待解决的问题并对将来的研究方向进行了展望.     

基于深度残差网络图像分类算法研究综述

近年来,由于计算机技术的飞速迅猛发展,特别是硬件条件的改善,计算能力不断提高,深层神经网络训练的时间大大缩短,深度残差网络也迅速成为一个新的研究热点.深度残差网络作为一种极深的网络架构,在精度和收敛等方面都展现出了很好的特性.研究者们深入研究其本质并在此基础上提出了很多关于深度残差网络的改进,如宽残差网络,金字塔型残差网络,密集型残差网络,注意力残差网络等等.本文从残差网络的设计出发,分析了不同残差单元的构造方式,介绍了深度残差网络不同的变体.从不同的角度比较了不同网络之间的差异以及这些网络架构在常用图像分类数据集上的性能表现.最后我们对于这些网络进行了总结,并讨论了未来深度残差网络在图像分类领域的一些研究方向.     

基于分段模糊Lyapunov函数的模糊系统稳定性分析和保性能设计

针对一类 Takagi-Sugeno (T-S) 连续模糊系统, 在分析模糊系统前提规则结构信息的基础上, 研究了其稳定性和保性能设计问题. 通过将模糊 Lyapunov 函数 (FLF) 和分段二次 Lyapunov 函数 (PQLF) 结合, 构造出分段模糊 Lyapunov 函数 (PFLF), 并提出了一种新的并行分配补偿 (PDC) 控制器. 基于 PFLF 方法, 得到了线性矩阵不等式 (LMI) 形式的模糊系统分析与设计的求解方法. 该方法继承了 FLF 与 PQLF 的优点. 仿真实例表明: 该方法所得稳定性判据更为宽松, 具有更好的保性能控制效果.     

La9.33Si6O26基氧离子导电复合材料的制备与导电性

采用改性共沉淀法合成了La9.33Si6O26-10wt%Zr0.86Y0.14O1.92两相共存的氧离子导电复合材料,利用X射线衍射、扫描电子显微镜、交流阻抗技术分别表征了材料的相组成、微观组织和离子导电性.结果表明,复合材料粉体平均晶粒尺寸为35 nm,烧结块体的平均颗粒尺寸为500 nm;在300～700℃温度范围内,复合材料的导电率均高于La9.33Si6O26或Zr0.86Y0.14O1.92单相材料,且700℃时比La9.33Si6O26高出1个数量级.结合交流阻抗谱及电模量谱对复合材料的导电机理进行了分析讨论.     

Facile preparation of poly(N-isopropylacrylamide)-based hydrogels via aqueous Diels-Alder click reaction

The study reports a facile method of preparing poly(N-isopropylacrylamide)- based hydrogels by means of the Diels-Alder reaction. First, polymeric dienes were synthesized by free radical copolymerization between N-isopropylacrylamide (NIPA) and furfuryl methacrylate (FM), with 2, 2′-azobisisobutyronitrile (AIBN) as an initiator, and polymeric dienophile was obtained by a coupling reaction of poly(ethylene glycol) (PEG) and N-maleoyl-l-leucine (LMI) under N, N′-dicyclohexylcarbodiimide (DCC). Afterwards, the resultant dienes and dienophiles were dissolved in water and put in a refrigerator remaining a temperature of 9 °C, gelation via Diels-Alder reaction was observed after some time. The samples obtained at different steps were characterized by FTIR, NMR, GPC, SEM, CD, etc. It was found that LCST of copolymers decreases with the increase of FM content in copolymers. And the disassembly time of the hydrogels is closely related to the temperature and the solvents used. The swelling behavior study by gravimetric measurement indicates the hydrogels possess thermosensitivity and exhibit considerable swelling in water. Due to the simplicity of synthesis and no need for initiator or catalyzer and organic solvent, the strategy described here could find a promising application in the preparation of hydrogels.